The present invention relates to a process for forming a unitary workpiece from two independent parts and in particular to the formation of workpieces of this type in which the individual parts are of different materials, and wherein at least one of the parts is to be forged into a desired shape.
In British Pat. No. 1,265,137 a shaft and a gearwheel of different materials but each made by smelt-metallurgical methods are joined together in a forging process. It is also known from British Pat. No. 960,013 to unite a shaft and a wheel of the same grade of material by the common up-setting of the components, under the action of a forming closure. In this process locally confined resistance welding is possible in the junction zone, without any significant flow of material taking place.
U.S. Pat. No. 3,678,558 illustrates the production of gearwheels from two finished preformed components. In this process a gearwheel manufactured by powder-metallurgy is joined to a gearwheel manufactured by smelt-metallurgy by welding or adhering the parts without any resultant change in the form of the gearwheels. U.S. Pat. No. 3,727,999 illustrates the production of a bevel-gear formed of two correspondingly shaped rings, one fitted inside the other. Each of the rings were manufactured separately by powder-metallurgy processes and each had an alloy composition adapted to absorb different stresses. After formation of each of the rings, they were united together in a pressing process. If desired a still further consolidation could be accomplished by a subsequent hot-forging.
Finally, it is known from U.S. Pat. No. 3,772,935 to produce workpieces having differently stressed surfaces by separately placing together two powdered metals of different composition in a mold. The two layers of powder being thereafter pressed together and sintered.
As opposed to the complex and limited processes of the prior art, the present invention provides a process by which components of different materials may be simply and economically joined in a hole-and-plug connection, having a strong welded or bonded juncture, and simultaneously forged with a desired finished shape and in particular providing for an economical combination of simple and complicated forms of workpieces taking into account the differing demands to be placed on the properties of the materials.